LETTER TO THE EDITOR
Improvement of myocardial blood flow to ischemic regions by angiotensin-converting enzyme inhibition
Giancarlo Longobardi, MDa,1,
Nicola Ferrara, MD,
Giuseppe Furgi, MD,
Pasquale Abete, MD and
Franco Rengo, MD
a Fondazione Salvatore Maugeri, IRCCS, Centro Medico di Telese Terme, Divisione di Cardiologia, Via Bagni Vecchi 82037 Telese Terme (BN), Italy
Schneider et al. (1) analyzed the effects of acute angiotensin-converting enzyme (ACE) inhibition on myocardial blood flow (MBF) in ischemic and nonischemic regions of 10 symptomatic patients with coronary artery disease (CAD). They used [15O] water positron emission tomography at rest and during maximal dobutamine stress before and after angiotensin converting enzyme (ACE) inhibition and demonstrated that quinaprilat 10 mg intravenous was able to improve MBF to ischemic regions in patients with CAD.
There is some experimental and clinical evidence that ACE inhibitors can increase regional oxygen supply to ischemic areas of myocardium through a redistribution of regional blood flow in humans and animals (2–7). However, there is not evidence that ACE-inhibitors are able to improve the main clinical outcomes in evaluation of anti-ischemic efficacy of cardiovascular drugs as angina, ST segment depression and echocardiographic wall motion abnormalities during exercise or pharmacological stress test. In this regard we demonstrated, using exercise and dipyridamole echocardiographic stress tests, that neither captopril nor enalapril (sulfhydryl and not sulfhydryl ACE-inhibitors, respectively) had a significant antiischemic effect in patients with stable angina pectoris (8).
In our point of view, the main questions are: Has the improvement of MBF induced by acute administration of quinaprilat a clinical significance? Is it useful to evaluate the effects of a cardiovascular drug by an advanced technique as [15O] water positron emission tomography without the evidence of clinical, mechanical or electrocardiographic markers of myocardial ischemia in all patients during stress test?
Analyzing the methods used by authors (1), we found that most patients did not have clinical, electrocardiographic or mechanical criteria of ischemia during dobutamine stress test. Therefore, there is not evidence in the results section that the quinaprilat is able to reduce myocardial ischemia. This restricts the relevance of the conclusions for the average clinical reader. We think that the quinaprilat-induced changes in MBF are not enough to establish whether ACE-inhibitors are the anti-ischemic drugs or not.
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Footnotes
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1 glongobardi.fsm.it 
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References
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1. Schneider CA, Voth E, Moka D, et al. Improvement of myocardial blood flow to ischemic regions by angiotensin-converting enzyme inhibition with quinaprilat intravenous. J Am Coll Cardiol. 1999;34:1005–1011[Abstract/Free Full Text]
2. Ertl G, Kloner RA, Alexander RW, Braunwald E. Limitation of experimental infarct size by angiotensin-converting enzyme inhibitor. Circulation. 1982;65:40–48[Free Full Text]
3. Noguchi K, Kato T, Ito H, Aniya Y, Sakanashi M. Effect of intracoronary captopril on coronary blood flow and regional myocardial function in dogs. Eur J Pharmacol. 1985;110:11–19[Medline]
4. Gasic S, Dutczak R, Korn A, Kleinbloesem C. Angiotensin-converting enzyme inhibition with cilazapril improves myocardial perfusion to the ischemic regions during exercise: a pilot study. J Cardiovasc Pharmacol. 1990;15:227–232[Medline]
5. Piana RM, Wang SY, Friedmann M, Selke FW. Angiotensin-converting enzyme inhibition preserves endothelium-dependent coronary microvascular responses during short-term ischemia reperfusion. Circulation. 1996;93:544–551[Abstract/Free Full Text]
6. Ikram H, Low CJS, Shirlaw T, et al. Antianginal, hemodynamic and coronary vascular effects of captopril in stable angina pectoris. Am J Cardiol. 1990;66:164–167[CrossRef][Medline]
7. Kiowski W, Zuber M, Elsasser S, et al. Coronary vasodilation and improved myocardial lactate metabolism after angiotensin-converting enzyme inhibition with cilazapril in patients with congestive heart failure. Am Heart J. 1991;122:1382–1388[CrossRef][Medline]
8. Longobardi G, Ferrara N, Leosco D, et al. Failure of protective effect of captopril and enalapril on exercise and dipyridamole-induced myocardial ischemia. Am J Cardiol. 1995;76:255–258[Medline]
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